After writing this comment I thought of the 1933 novel When Worlds Collide co-written by Philip Wylie and Edwin Balmer.

South African astronomer Sven Bronson discovers that a pair of rogue planets, Bronson Alpha and Bronson Beta, will soon enter the solar system. In eight months, they will pass close enough to cause catastrophic damage to the Earth. Sixteen months later, after swinging around the Sun, Bronson Alpha will return to pulverize the Earth and leave. It is hoped that Bronson Beta will remain and assume a stable orbit.

Wikipedia describes the catastrophic damage from the first pass in the novel as

Tidal waves sweep inland at a height of 750 feet (230 m), volcanic eruptions and earthquakes add to the deadly toll, and the weather runs wild for more than two days. As a token of things to come, Bronson Alpha grazes and destroys the Moon.

Is it known if the authors drew upon the known science of the day to hypothesize what the effects of a planetary near approach would be like? I know it's nearly 100 years ago, but I'm curious how they came up with the science behind the induced tidal waves, and volcanos and earthquakes. The Moon grazing means the approach of at least one of the planets to Earth was less than 400,000 km, so if they'd assumed a mass for the planets, they could estimate quantitatively the forces on the Earth.

The fact that Bronson Alpha and Beta split up and have different, well described orbits suggests they'd certainly put some thought into the orbital mechanics, but I don't know if the orbits are realistic, nor if it was Earth's gravity or the interaction with the Moon that split Alpha and Beta. Is it known to what level of detail they had pursued all of the physics involved in the catastrophic damage and planet trajectories?

  • @user14111 aha, a datapoint! If you can find a way to post a quote and cite the essay, either in a partial answer or comment, I would really appreciate it! I'd love to read anything about it possible. Thanks! – uhoh Jan 25 '19 at 3:09
  • @user14111 great stuff, thank you! If nothing more definitive turns up in the next 2 days I would like to be able to accept this as an answer, as long as a source for the Moskowitz quotes can be cited. – uhoh Jan 25 '19 at 3:28

Sam Moskowitz, prominent old-time fan and historian of science fiction, wrote an essay on Philip Wylie in his Studies in Science Fiction series. Titled "Philip Wylie: The Saccharine Cynic", it was originally published in Fantastic Science Fiction Stories, September 1960, available at the Internet Archive; it was reprinted (without the subtitle) in Science Fantasy, October 1961, also available at the Internet Archive.

According to Moskowitz, Wylie considered himself a stickler for scientific accuracy (his collaborator Edwin Balmer not so much), and consulted some unnamed friends at Caltech about the physics of When Worlds Collide.

A bug on astronomy, Balmer had roughed out a sequence of events for a novel where two planets enter our solar system from outer space. One will strike the earth with resultant mutual destruction. The only chance man has for survival is to build space ships and transfer a few thousand men and women to the second invading world — which will take up an orbit around the sun — before it moves out of range. He presented this idea to Wylie and found a kindred spirit. Like a child with a new toy, Philip Wylie assembled his physicist friends at Cal Tech and mathematically mapped out the scientific elements by which this feat of [spacial] leap frog could be accomplished. The time lost in the advancement of atomics was unquestionably science fiction's gain.

The collaboration, written as These Shall Not Die, was retitled When Worlds Collide by Donald Kennicott and opened in the September, 1932 issue of BLUE BOOK.

[. . . .]

There seemed no question that a third book in the series, solving the riddle of the new planet's missing inhabitants was the next logical step, and indeed a plot was outlined by Balmer but vetoed by Wylie. Every word of When Worlds Collide had been written by Wylie and it had been published as written. Similarly, Wylie wrote all of the text of the sequel, but before press time Balmer made some alterations that affected scientific plausibility. Wylie, a purist at science fiction nurtured in the tradition of Jules Verne, H. G. Wells and Hugo Gernsback, was disturbed by these changes. Balmer's plot outline of the third book would have been difficult to validate on the basis of known facts. Wylie contended that the success of the first two volumes was predicated, to a large extent, upon the high degree of respect shown for scientific accuracy. Therefore, though he continued to collaborate with Balmer on adventure and detective novels, he refused to give literary substance to the projected third in the When Worlds Collide series.

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    I don't care how many "physicists" worked on the math; the trajectory fails simple tests of common sense. 1I/2017 U1 ('Oumuamua) had a velocity at 1AU of c.50km/s and spent a total of just 2 months at a distance of less than 1 AU from the sun. The Bronson bodies already had a velocity at Saturn's orbital distance of at least 80km/s (Ch.3, from Neptune to Saturn in about 11 mo) and so could not have taken more than 2 months between crossings of Earth's orbit. – DavidW Jan 25 '19 at 19:56
  • @DavidW this is really intriguing! I'm going to have to locate a copy in Taipei and read it now. – uhoh Jan 26 '19 at 14:38

Actually, they both get the collision itself completely wrong. Let me elaborate.

In the novel, Wylie and Balmer describe the collision of Earth and Bronson Alpha as "decillions of tons of mass colliding in cosmic catastrophe". A little later, they describe shattered fragments of the Earth assuming stable orbits of their own around the Sun. First of all, real planets simply do not behave in this fashion when they come within several million miles of each other, let alone on a collision course. And if it's the latter, they certainly do not still retain their original solid, pre-collision, shape.

How do I know this? Two simple words: tidal forces! Any celestial body the size of the Earth, if acted upon by the enormous gravity of another celestial body the size of Bronson Alpha, would immediately start to distend itself grotesquely in the direction of the approaching other body until it assumed an egg-shape with the pointy end in the direction of the other body. And vice versa ala Alpha. It, too, would immediately distend itself towards Earth and assume an egg-shape of its own.

So what you would have would be two giant egg-shaped planetary bodies being slowly ripped apart by unbelievably powerful tidal forces long before they ever got within even one moon orbit's distance from each other, let alone physically colliding like two intact cosmic billiard balls in space, like in the novel. Celestial physics simply will not permit this.

Which further means that no one will ever be able to save themselves from such an imminent catastrophe in time to be decisive. The entire world would have been ripped to pieces without actually colliding with the other planet at all. Worse, the Earth would have already completely melted, perhaps even been vaporized, by said tidal forces, before even being ripped apart, because of latent heat. And obviously, the other body would not be immune to these effects either.

In the end, our precious Earth (and Alpha) would be reduced by the combined effect of the two planets' tidal forces upon each other to a vast cloud of floating rock vapor in space which could conceivably re-coalesce into a brand new planet twice the size of the original Earth, given enough time. But, of course, no one would be around anymore to take advantage of this!

Just thought I'd point out this little, not-so-nit-picky, detail to anyone reading this site because it's something that's always bothered me about the novel. The end of the world, if it ever does happen, won't be anywhere near as neat and orderly as Wylie and Balmer imagined. It'll actually be way, way worse! And unlike the famous REM song, we will most definitely not be feeling fine!

Other than that, I actually really loved the book and consider it, sans collision, to be perhaps the single greatest sci-fi book ever written anywhere by anyone.

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    Hi, welcome to SF&F. You have some good points, though your post could use more paragraphs and fewer exclamation marks. :) Unfortunately, this does not appear to be the kind of answer the person posting the question wants to hear, so it may not be well-received. You could make this a better answer by providing some rough approximations, for example of how much tidal heating would occur just to demonstrate your argument is based in real-world physics. – DavidW May 4 '20 at 19:32
  • I'm " the person posting the question" and this would be more "the kind of answer" I'd "wants to hear" if it were a little more quantitative. In this answer I calculated that the tidal forces on Earth at the moment of contact with Jupiter would be 0.4 g on the side facing Jupiter, which is not enough to "tear the Earth apart" or even lift small objects off of the surface. That's because Earth's center of mass would be accelerating towards Jupiter at roughly 2 g already. – uhoh May 4 '20 at 21:17
  • If you reached out and tried to hold the Earth's center of mass in place, then Jupiter's gravity would pull the rest of the Earth apart. But as a free body in space, the gradient of Jupiter's gravity alone would not do that. I don't know Bronson Alpha's radius and mass is nor the distance of closest approach, and the fact that those numbers don't appear in your answer means it's unfounded speculation. It seems to me that it's more like "I always wanted to say this so here it goes" than it is an answer to the question as asked. Welcome to Stack Exchange! – uhoh May 4 '20 at 21:20
  • But if you'd like to add those three numbers to your answer then we could work it out, but it would have to be in a context remaining close to the goal of providing an answer to the question as asked. – uhoh May 4 '20 at 21:22
  • Thank you all for your prescient comments regarding my admittedly rather convoluted explanation concerning the likely physical effects of a cosmic collision between Earth and another much larger planet. Good points, all. I'm sorry if my answer wasn't more mathematically quantitative. My higher math skills are somewhat lacking in equational coherence, particularly as they pertain to celestial mechanics. But I promise you all I'm going to bone up on that real soon! Consider today's interesting, if mathematically unfounded, explanation of mine a test case. I will get better at this. Thanks. – Daniel Farabee May 5 '20 at 0:32

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